this.hideDropMarker = function() {
  var dropMarker = document.getAnonymousElementByAttribute(this, "class", "toolbarbutton-menu-dropmarker");
  if (dropMarker) {
    dropMarker.setAttribute("hidden", "true");
  } else {
    setTimeout(function(self) {self.hideDropMarker();}, 100, this);
  }
}
this.hideDropMarker();